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<head><meta charset="utf-8"><title>meeting 2020-09-29 · wg-traits · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/index.html">wg-traits</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html">meeting 2020-09-29</a></h3>

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<a name="211674475"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211674475" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211674475">(Sep 29 2020 at 19:46)</a>:</h4>
<p>Hi <span class="user-group-mention" data-user-group-id="692">@WG-traits</span>!<br>
Meeting in ~15 minutes</p>



<a name="211674508"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211674508" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211674508">(Sep 29 2020 at 19:47)</a>:</h4>
<p>Agenda hackmd: <a href="https://hackmd.io/nrhN5A8sR2eY9UdfJTKcJg?both">https://hackmd.io/nrhN5A8sR2eY9UdfJTKcJg?both</a></p>



<a name="211676167"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676167" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676167">(Sep 29 2020 at 20:00)</a>:</h4>
<p>Ok <span class="user-group-mention" data-user-group-id="692">@WG-traits</span></p>



<a name="211676169"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676169" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676169">(Sep 29 2020 at 20:00)</a>:</h4>
<p>meeting time</p>



<a name="211676262"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676262" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676262">(Sep 29 2020 at 20:01)</a>:</h4>
<p>So, last week, we had hastily at the last minute confirmed/planned to discuss wellformedness this meeting</p>



<a name="211676298"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676298" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676298">(Sep 29 2020 at 20:01)</a>:</h4>
<p><em>but</em> a couple things have come up first</p>



<a name="211676319"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676319" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676319">(Sep 29 2020 at 20:01)</a>:</h4>
<p>Before that though, any annoucements?</p>



<a name="211676463"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676463" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676463">(Sep 29 2020 at 20:02)</a>:</h4>
<p>I don't have any :)</p>



<a name="211676515"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676515" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676515">(Sep 29 2020 at 20:02)</a>:</h4>
<p>Me neither</p>



<a name="211676534"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676534" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676534">(Sep 29 2020 at 20:03)</a>:</h4>
<p>Only one PR this week I think</p>



<a name="211676561"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676561" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676561">(Sep 29 2020 at 20:03)</a>:</h4>
<p>Fix for a bug introduced in the auto trait PR</p>



<a name="211676593"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676593" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676593">(Sep 29 2020 at 20:03)</a>:</h4>
<p>Okay, first item to discuss:</p>



<a name="211676604"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676604" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676604">(Sep 29 2020 at 20:03)</a>:</h4>
<p>rustc PR: <a href="https://github.com/rust-lang/rust/issues/77187">#77187</a></p>



<a name="211676631"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676631" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676631">(Sep 29 2020 at 20:03)</a>:</h4>
<p>This came up a few months ago</p>



<a name="211676645"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676645" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676645">(Sep 29 2020 at 20:03)</a>:</h4>
<p>But there's a new PR</p>



<a name="211676719"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676719" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676719">(Sep 29 2020 at 20:04)</a>:</h4>
<p>Basically the question is: how do we handle fundamental types with &gt;1 parameter</p>



<a name="211676764"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676764" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676764">(Sep 29 2020 at 20:04)</a>:</h4>
<p>oh</p>



<a name="211676765"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676765" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676765">(Sep 29 2020 at 20:04)</a>:</h4>
<p>ugh</p>



<a name="211676799"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676799" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676799">(Sep 29 2020 at 20:05)</a>:</h4>
<p>In that PR, they are Adding a <code>A = Global</code> param to <code>Box</code></p>



<a name="211676811"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676811" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676811">(Sep 29 2020 at 20:05)</a>:</h4>
<p>yeah</p>



<a name="211676834"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676834" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676834">(Sep 29 2020 at 20:05)</a>:</h4>
<p>I'm trying to think</p>



<a name="211676853"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676853" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676853">(Sep 29 2020 at 20:05)</a>:</h4>
<p>we all know what fundamental does? :)</p>



<a name="211676874"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676874" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676874">(Sep 29 2020 at 20:05)</a>:</h4>
<p>maybe useful to review regardless</p>



<a name="211676888"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676888" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676888">(Sep 29 2020 at 20:05)</a>:</h4>
<p>(how much do we want to dive into this topic now?)</p>



<a name="211676935"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211676935" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211676935">(Sep 29 2020 at 20:06)</a>:</h4>
<p>I think we should decide now some resolution to unblock that PR</p>



<a name="211677096"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677096" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677096">(Sep 29 2020 at 20:07)</a>:</h4>
<p>I sort of agree</p>



<a name="211677099"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677099" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677099">(Sep 29 2020 at 20:07)</a>:</h4>
<p>Even if that is "instead of asserting in Chalk, we will warn" or something like that</p>



<a name="211677121"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677121" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677121">(Sep 29 2020 at 20:07)</a>:</h4>
<p>Yeah I mean we can just make it a FIXME and that's probably fine</p>



<a name="211677138"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677138" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677138">(Sep 29 2020 at 20:07)</a>:</h4>
<p>but it might be worth talking out very briefly</p>



<a name="211677165"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677165" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677165">(Sep 29 2020 at 20:07)</a>:</h4>
<p>I think so</p>



<a name="211677280"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677280" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677280">(Sep 29 2020 at 20:08)</a>:</h4>
<p>I'm looking now why exactly we depend on only a single param</p>



<a name="211677303"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677303" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677303">(Sep 29 2020 at 20:08)</a>:</h4>
<p>the idea of a "fundamental type" is that you can, in a downstream crate, implement traits for it. So e.g.</p>
<div class="codehilite"><pre><span></span><code>struct MyType;
impl Debug for Box&lt;MyType&gt;
</code></pre></div>


<p>something like this is legal per the <em>orphan</em> check (as it happens, there is an impl <code>impl&lt;T&gt; Debug for Box&lt;T&gt;</code> so it will fail the <em>overlap</em> check)</p>



<a name="211677342"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677342" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677342">(Sep 29 2020 at 20:09)</a>:</h4>
<p>but in contrast something like <code>impl Debug for Vec&lt;MyType&gt;</code> would fail the orphan check</p>



<a name="211677360"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677360" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677360">(Sep 29 2020 at 20:09)</a>:</h4>
<p>i.e., the rule that says "you can only implement an upstream trait for a local type"</p>



<a name="211677382"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677382" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677382">(Sep 29 2020 at 20:09)</a>:</h4>
<p>in other words, <code>Box&lt;LocalType&gt;</code> is considered local to your crate</p>



<a name="211677405"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677405" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677405">(Sep 29 2020 at 20:09)</a>:</h4>
<p>this is because <code>Box</code> is <em>fundamental</em>, along with <code>&amp;</code> and a few other type constructors</p>



<a name="211677504"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677504" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677504">(Sep 29 2020 at 20:10)</a>:</h4>
<p>(an implication of this is that adding a blanket impl of a trait for <code>Box&lt;T&gt;</code> is a semver breaking change)</p>



<a name="211677543"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677543" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> detrumi <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677543">(Sep 29 2020 at 20:10)</a>:</h4>
<p>Hm. And rustc can handle multiple type params there, and chalk can't?</p>



<a name="211677550"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677550" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677550">(Sep 29 2020 at 20:10)</a>:</h4>
<p>probably the best explanation of this is <a href="https://github.com/rust-lang/rfcs/blob/master/text/2451-re-rebalancing-coherence.md">RFC 2451</a></p>



<a name="211677579"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677579" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677579">(Sep 29 2020 at 20:11)</a>:</h4>
<p>(huzzah sgrif)</p>



<a name="211677602"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677602" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677602">(Sep 29 2020 at 20:11)</a>:</h4>
<p>For reference: this is where Chalk fails: <a href="https://github.com/rust-lang/chalk/blob/2d086ba33f1f7f5e952d5f98fdf862777729da9f/chalk-solve/src/clauses/program_clauses.rs#L412">https://github.com/rust-lang/chalk/blob/2d086ba33f1f7f5e952d5f98fdf862777729da9f/chalk-solve/src/clauses/program_clauses.rs#L412</a></p>



<a name="211677616"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677616" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677616">(Sep 29 2020 at 20:11)</a>:</h4>
<p>yeah so I imagine what rustc says is that, e.g., <code>Box&lt;u32, MyType&gt;</code> (for example) is <em>not</em> local</p>



<a name="211677624"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677624" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677624">(Sep 29 2020 at 20:11)</a>:</h4>
<p>but let's check that first</p>



<a name="211677668"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677668" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677668">(Sep 29 2020 at 20:11)</a>:</h4>
<p>I would expect <code>Box&lt;u32, MyType&gt;</code> to be local here</p>



<a name="211677717"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677717" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677717">(Sep 29 2020 at 20:12)</a>:</h4>
<p>at least from the last time I looked at the coherence implementation</p>



<a name="211677736"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677736" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677736">(Sep 29 2020 at 20:12)</a>:</h4>
<p>I might be misremembering this though, so better double check <span aria-label="sweat smile" class="emoji emoji-1f605" role="img" title="sweat smile">:sweat_smile:</span></p>



<a name="211677842"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677842" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677842">(Sep 29 2020 at 20:13)</a>:</h4>
<p>I would imagine that for any <code>U</code>, <code>Box&lt;T, U&gt;</code> is local if <code>T</code> is local</p>



<a name="211677918"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677918" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677918">(Sep 29 2020 at 20:14)</a>:</h4>
<p>I guess that probably makes the most sense</p>



<a name="211677931"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677931" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677931">(Sep 29 2020 at 20:14)</a>:</h4>
<p>basically if "any part" is local, then the type clearly can't have been written in an upstream crate</p>



<a name="211677947"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677947" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677947">(Sep 29 2020 at 20:14)</a>:</h4>
<p>my expectation is that as long as <code>T</code> is not an uncovered ty param box <code>Box&lt;T, local&gt;</code> is local</p>



<a name="211677958"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211677958" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211677958">(Sep 29 2020 at 20:14)</a>:</h4>
<p>and hence could only be matched by a blanket impl</p>



<a name="211678024"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678024" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678024">(Sep 29 2020 at 20:15)</a>:</h4>
<p>ok so</p>



<a name="211678036"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678036" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678036">(Sep 29 2020 at 20:15)</a>:</h4>
<p>on the <em>chalk</em> side of things</p>



<a name="211678136"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678136" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678136">(Sep 29 2020 at 20:16)</a>:</h4>
<p>we define this stuff via a few special goals</p>



<a name="211678147"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678147" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678147">(Sep 29 2020 at 20:16)</a>:</h4>
<p><code>IsLocal</code></p>



<a name="211678152"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678152" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678152">(Sep 29 2020 at 20:16)</a>:</h4>
<p><code>IsUpstream</code></p>



<a name="211678199"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678199" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678199">(Sep 29 2020 at 20:16)</a>:</h4>
<p>and <code>DownstreamType</code></p>



<a name="211678242"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678242" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678242">(Sep 29 2020 at 20:16)</a>:</h4>
<p><a href="https://github.com/rust-lang/chalk/blob/2d086ba33f1f7f5e952d5f98fdf862777729da9f/chalk-solve/src/clauses/program_clauses.rs#L330-L377">code here</a></p>



<a name="211678323"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678323" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678323">(Sep 29 2020 at 20:17)</a>:</h4>
<p>if we want to encode that intuition then presumably we would update this code:</p>
<div class="codehilite" data-code-language="Rust"><pre><span></span><code><span class="w">    </span><span class="sd">/// forall&lt;T&gt; { IsLocal(Box&lt;T&gt;) :- IsLocal(T). }</span>
<span class="w">    </span><span class="sd">///</span>
<span class="w">    </span><span class="sd">/// forall&lt;T&gt; { IsUpstream(Box&lt;T&gt;) :- IsUpstream(T). }</span>
<span class="w">    </span><span class="sd">///</span>
<span class="w">    </span><span class="sd">/// // Generated for both upstream and local fundamental types</span>
<span class="w">    </span><span class="sd">/// forall&lt;T&gt; { DownstreamType(Box&lt;T&gt;) :- DownstreamType(T). }</span>
</code></pre></div>



<a name="211678330"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678330" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678330">(Sep 29 2020 at 20:17)</a>:</h4>
<p>to something like</p>



<a name="211678419"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678419" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678419">(Sep 29 2020 at 20:18)</a>:</h4>
<div class="codehilite"><pre><span></span><code>forall&lt;T, U&gt; { IsLocal(Box&lt;T&gt;) :- IsLocal(T) }
forall&lt;T, U&gt; { IsLocal(Box&lt;T&gt;) :- IsLocal(U) }
</code></pre></div>



<a name="211678461"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678461" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678461">(Sep 29 2020 at 20:18)</a>:</h4>
<div class="codehilite"><pre><span></span><code>forall&lt;T, U&gt; { IsUpstream(Box&lt;T, U&gt;) :- IsUpstream(T), IsUpstream(U) }
</code></pre></div>



<a name="211678481"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678481" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678481">(Sep 29 2020 at 20:18)</a>:</h4>
<p>That seems right to me</p>



<a name="211678531"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678531" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678531">(Sep 29 2020 at 20:19)</a>:</h4>
<div class="codehilite"><pre><span></span><code>forall&lt;T, U&gt; { DownstreamType(Box&lt;T, U&gt;) :- DownstreamType(T). }
forall&lt;T, U&gt; { DownstreamType(Box&lt;T, U&gt;) :- DownstreamType(U). }
</code></pre></div>



<a name="211678544"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678544" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678544">(Sep 29 2020 at 20:19)</a>:</h4>
<p>that last one... is interesting</p>



<a name="211678586"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678586" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678586">(Sep 29 2020 at 20:19)</a>:</h4>
<p>the role of <code>DownstreamType</code> as I recall is to generate a kind of "placeholder-like" type representing <em>some</em> type defined in a downstream crate</p>



<a name="211678606"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678606" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678606">(Sep 29 2020 at 20:19)</a>:</h4>
<p>I was about to ask about that</p>



<a name="211678684"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678684" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678684">(Sep 29 2020 at 20:20)</a>:</h4>
<p>I am trying to find what docs we wrote :)</p>



<a name="211678808"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678808" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678808">(Sep 29 2020 at 20:21)</a>:</h4>
<p>There's not many docs on coherence</p>



<a name="211678830"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678830" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678830">(Sep 29 2020 at 20:21)</a>:</h4>
<p>I feel like <span class="user-mention" data-user-id="117350">@Sunjay Varma</span> wrote some beautiful docs</p>



<a name="211678851"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678851" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678851">(Sep 29 2020 at 20:21)</a>:</h4>
<p>maybe they are still around in a dropbox paper document or something</p>



<a name="211678855"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678855" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678855">(Sep 29 2020 at 20:21)</a>:</h4>
<p>and we can import them into the chalk book</p>



<a name="211678873"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678873" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678873">(Sep 29 2020 at 20:22)</a>:</h4>
<p>I thought you had a blog post about this</p>



<a name="211678919"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678919" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678919">(Sep 29 2020 at 20:22)</a>:</h4>
<p>Maybe I'm misremembering</p>



<a name="211678931"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678931" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678931">(Sep 29 2020 at 20:22)</a>:</h4>
<p>I don't think I ever wrote about the <em>chalk-ification</em> of the coherence rules</p>



<a name="211678981"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678981" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678981">(Sep 29 2020 at 20:22)</a>:</h4>
<p>Okay, so: who wants to make a PR for this?</p>



<a name="211678995"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211678995" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211678995">(Sep 29 2020 at 20:23)</a>:</h4>
<p>It seems like it would be pretty simple</p>



<a name="211679003"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679003" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679003">(Sep 29 2020 at 20:23)</a>:</h4>
<p>anyway I think I would be happy to see the rules I described above, and we should open an issue to track it</p>



<a name="211679019"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679019" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679019">(Sep 29 2020 at 20:23)</a>:</h4>
<p>I think the coherence rules probably need some love anyway</p>



<a name="211679024"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679024" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Sunjay Varma <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679024">(Sep 29 2020 at 20:23)</a>:</h4>
<p>I think I always meant to write something but never had a chance. Here's my doc with all my notes if anyone else wants to pick it up: <a href="https://paper.dropbox.com/doc/Chalk-Coherence--A8hYREfV30eyU8YNbvxnxhwLAQ-rxgcvrmxv0yNwHvOpg326">https://paper.dropbox.com/doc/Chalk-Coherence--A8hYREfV30eyU8YNbvxnxhwLAQ-rxgcvrmxv0yNwHvOpg326</a></p>



<a name="211679040"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679040" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679040">(Sep 29 2020 at 20:23)</a>:</h4>
<p>ah thank you  <span class="user-mention" data-user-id="117350">@Sunjay Varma</span> <span aria-label="heart" class="emoji emoji-2764" role="img" title="heart">:heart:</span></p>



<a name="211679071"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679071" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Sunjay Varma <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679071">(Sep 29 2020 at 20:23)</a>:</h4>
<p>No worries. Sorry I never had a chance to finish that up! <span aria-label="sweat smile" class="emoji emoji-1f605" role="img" title="sweat smile">:sweat_smile:</span></p>



<a name="211679081"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679081" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679081">(Sep 29 2020 at 20:23)</a>:</h4>
<p>I think we should import that straight into the chalk book as is</p>



<a name="211679098"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679098" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679098">(Sep 29 2020 at 20:23)</a>:</h4>
<p>Agreed</p>



<a name="211679102"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679102" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679102">(Sep 29 2020 at 20:23)</a>:</h4>
<p>and we can improve it iteratively</p>



<a name="211679192"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679192" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679192">(Sep 29 2020 at 20:24)</a>:</h4>
<p>Okay, I will open an issue after this meeting. And a PR to import that into chalk book tonight.</p>



<a name="211679223"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679223" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679223">(Sep 29 2020 at 20:24)</a>:</h4>
<p>If by Friday someone hasn't opened a PR for the coherence rules, I will</p>



<a name="211679239"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679239" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679239">(Sep 29 2020 at 20:24)</a>:</h4>
<p>(maybe before, but it's a busy week)</p>



<a name="211679297"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679297" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679297">(Sep 29 2020 at 20:25)</a>:</h4>
<p>the biggest problem will probably be that dropbox paper generates such terrible markdown</p>



<a name="211679317"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679317" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679317">(Sep 29 2020 at 20:25)</a>:</h4>
<p>sad</p>



<a name="211679423"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679423" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679423">(Sep 29 2020 at 20:26)</a>:</h4>
<p>I'll  try to format it as best as possible</p>



<a name="211679446"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679446" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679446">(Sep 29 2020 at 20:26)</a>:</h4>
<p>Ok, let's move on</p>



<a name="211679448"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679448" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679448">(Sep 29 2020 at 20:26)</a>:</h4>
<p>yeah I wouldn't let perfect be enemy of the good here for sure</p>



<a name="211679504"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679504" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679504">(Sep 29 2020 at 20:26)</a>:</h4>
<p>Next topic is on the binder refactor in rustc</p>



<a name="211679515"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679515" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679515">(Sep 29 2020 at 20:26)</a>:</h4>
<p>That I've been chipping away at</p>



<a name="211679519"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679519" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679519">(Sep 29 2020 at 20:26)</a>:</h4>
<p>(<a href="https://github.com/rust-lang/rust/issues/76814">#76814</a>)</p>



<a name="211679558"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679558" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679558">(Sep 29 2020 at 20:27)</a>:</h4>
<p>Basically, the first pass, there was some really bad performance</p>



<a name="211679593"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679593" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679593">(Sep 29 2020 at 20:27)</a>:</h4>
<p>So, I've been trying to move a bunch of <code>bind</code>s to <code>rebind</code>s</p>



<a name="211679615"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679615" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679615">(Sep 29 2020 at 20:27)</a>:</h4>
<p>Where <code>rebind</code> is essentially like Chalk's <code>Binders::new</code></p>



<a name="211679622"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679622" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679622">(Sep 29 2020 at 20:27)</a>:</h4>
<p>yeah that was my hunch</p>



<a name="211679646"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679646" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679646">(Sep 29 2020 at 20:28)</a>:</h4>
<p>well wait</p>



<a name="211679691"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679691" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679691">(Sep 29 2020 at 20:28)</a>:</h4>
<p>I think I remember thinking that a lot of the <code>map</code> calls</p>



<a name="211679700"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679700" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679700">(Sep 29 2020 at 20:28)</a>:</h4>
<p>In that you must pass the number of bound vars (and in the future the actual onces)</p>



<a name="211679706"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679706" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679706">(Sep 29 2020 at 20:28)</a>:</h4>
<p>probably didn't change the number of variables</p>



<a name="211679723"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679723" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679723">(Sep 29 2020 at 20:28)</a>:</h4>
<p>Right</p>



<a name="211679769"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679769" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679769">(Sep 29 2020 at 20:28)</a>:</h4>
<p>Basically, there's a <em>lot</em> of places in rustc where there is a <code>skip_binders()</code> followed closely by a <code>bind</code></p>



<a name="211679815"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679815" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679815">(Sep 29 2020 at 20:29)</a>:</h4>
<p>Unfortunately, some of that is due to the current shakeup around <code>Predicate::Forall</code></p>



<a name="211679948"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211679948" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211679948">(Sep 29 2020 at 20:30)</a>:</h4>
<p>Now, the question I had was:</p>



<a name="211680003"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680003" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680003">(Sep 29 2020 at 20:30)</a>:</h4>
<p>Is it worth adding such a function <code>rebind</code> to rustc <em>without</em> actually tracking bound vars</p>



<a name="211680034"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680034" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680034">(Sep 29 2020 at 20:30)</a>:</h4>
<p>on the basis of there only being a semantic difference</p>



<a name="211680036"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680036" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680036">(Sep 29 2020 at 20:30)</a>:</h4>
<p>I don't quite get what <code>rebind</code> does</p>



<a name="211680060"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680060" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680060">(Sep 29 2020 at 20:31)</a>:</h4>
<p>maybe I have to refresh my memory of <code>Binders::new</code></p>



<a name="211680080"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680080" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680080">(Sep 29 2020 at 20:31)</a>:</h4>
<p>So, in my branch, <code>bind</code> goes through and counts the bound vars to store</p>



<a name="211680089"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680089" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680089">(Sep 29 2020 at 20:31)</a>:</h4>
<p><code>rebind</code>, you pass that</p>



<a name="211680131"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680131" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680131">(Sep 29 2020 at 20:31)</a>:</h4>
<p>In Chalk, you can either create a <code>Binders</code> by passing the VariableKinds, or have it empty</p>



<a name="211680156"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680156" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680156">(Sep 29 2020 at 20:31)</a>:</h4>
<p>there's no option for Chalk to "visit" the value and collect them</p>



<a name="211680234"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680234" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680234">(Sep 29 2020 at 20:32)</a>:</h4>
<p>let me just link the code</p>



<a name="211680242"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680242" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680242">(Sep 29 2020 at 20:32)</a>:</h4>
<p>I see</p>



<a name="211680265"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680265" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680265">(Sep 29 2020 at 20:32)</a>:</h4>
<p>so you're finding that you often (sometimes?) know the number in advance, essentially?</p>



<a name="211680312"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680312" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680312">(Sep 29 2020 at 20:33)</a>:</h4>
<p>Usually, yes!</p>



<a name="211680321"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680321" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680321">(Sep 29 2020 at 20:33)</a>:</h4>
<p>Because we just did a <code>skip_binders()</code></p>



<a name="211680352"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680352" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680352">(Sep 29 2020 at 20:33)</a>:</h4>
<p>I see</p>



<a name="211680363"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680363" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680363">(Sep 29 2020 at 20:33)</a>:</h4>
<p>and this can't be structured as a <code>map</code> for one reason or another</p>



<a name="211680368"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680368" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680368">(Sep 29 2020 at 20:34)</a>:</h4>
<p>Right</p>



<a name="211680417"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680417" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680417">(Sep 29 2020 at 20:34)</a>:</h4>
<p>Let me give an example</p>



<a name="211680457"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680457" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680457">(Sep 29 2020 at 20:34)</a>:</h4>
<p>(also, <a href="https://github.com/rust-lang/rust/pull/76814/files#diff-dae5090f4552c45ff2d296ef9c61ecd9R949">relevant</a> code for bind)</p>



<a name="211680546"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680546" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680546">(Sep 29 2020 at 20:35)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/pull/76814/files#diff-8f7c8234d9e4b8a6b999a8539032942dR655">https://github.com/rust-lang/rust/pull/76814/files#diff-8f7c8234d9e4b8a6b999a8539032942dR655</a></p>



<a name="211680549"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680549" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680549">(Sep 29 2020 at 20:35)</a>:</h4>
<p>is an example</p>



<a name="211680676"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680676" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680676">(Sep 29 2020 at 20:36)</a>:</h4>
<p>/me clicks</p>



<a name="211680678"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680678" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680678">(Sep 29 2020 at 20:36)</a>:</h4>
<p>Basically, the idea of this is to start moving rustc into the direction of "being more aware of what we're doing around bound variables"</p>



<a name="211680702"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680702" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680702">(Sep 29 2020 at 20:36)</a>:</h4>
<p>yeah I figured it'd be something like this</p>



<a name="211680728"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680728" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680728">(Sep 29 2020 at 20:36)</a>:</h4>
<p>such an annoying pattern</p>



<a name="211680748"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680748" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680748">(Sep 29 2020 at 20:37)</a>:</h4>
<p>it feels like we should be able to do something more elegant :)</p>



<a name="211680756"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680756" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680756">(Sep 29 2020 at 20:37)</a>:</h4>
<p>but I can't think of anything</p>



<a name="211680763"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680763" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680763">(Sep 29 2020 at 20:37)</a>:</h4>
<p>me neither</p>



<a name="211680788"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680788" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680788">(Sep 29 2020 at 20:37)</a>:</h4>
<p>anyway, this feels <em>to me</em> like a cleaner setup, in that it is more explicit, though I wish we could make it "feel" a bit nicer</p>



<a name="211680803"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680803" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680803">(Sep 29 2020 at 20:37)</a>:</h4>
<p>like it's kind of nice to "link"</p>



<a name="211680809"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680809" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680809">(Sep 29 2020 at 20:37)</a>:</h4>
<p>I think I might <em>for ergonomics</em> change to</p>



<a name="211680883"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680883" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Areredify <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680883">(Sep 29 2020 at 20:38)</a>:</h4>
<p>I want this too</p>



<a name="211680889"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680889" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680889">(Sep 29 2020 at 20:38)</a>:</h4>
<p>This is also maybe MCP territory</p>



<a name="211680908"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680908" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680908">(Sep 29 2020 at 20:38)</a>:</h4>
<p>Well, almost certainly</p>



<a name="211680923"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680923" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680923">(Sep 29 2020 at 20:38)</a>:</h4>
<div class="codehilite" data-code-language="Rust"><pre><span></span><code><span class="n">bound_predicate</span><span class="p">.</span><span class="n">map</span><span class="p">(</span><span class="o">|</span><span class="n">_</span><span class="o">|</span><span class="w"> </span><span class="n">p</span><span class="p">)</span><span class="w"></span>
</code></pre></div>

<p>or  something like </p>
<div class="codehilite" data-code-language="Rust"><pre><span></span><code><span class="n">bound_predicate</span><span class="p">.</span><span class="n">with_value</span><span class="p">(</span><span class="n">p</span><span class="p">)</span><span class="w"></span>
</code></pre></div>



<a name="211680960"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680960" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680960">(Sep 29 2020 at 20:38)</a>:</h4>
<p>Oh, true</p>



<a name="211680994"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211680994" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211680994">(Sep 29 2020 at 20:39)</a>:</h4>
<p>but I would definitely land some PRs that adopted a style like that</p>



<a name="211681009"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681009" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681009">(Sep 29 2020 at 20:39)</a>:</h4>
<p>it's nice that it can be done progressively and in isolation</p>



<a name="211681010"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681010" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681010">(Sep 29 2020 at 20:39)</a>:</h4>
<p>Okay cool</p>



<a name="211681021"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681021" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681021">(Sep 29 2020 at 20:39)</a>:</h4>
<p>if you hounded me I could just r+ them extra fast ;)</p>



<a name="211681032"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681032" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681032">(Sep 29 2020 at 20:39)</a>:</h4>
<p>actually wait</p>



<a name="211681040"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681040" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681040">(Sep 29 2020 at 20:39)</a>:</h4>
<p>better yet is we get somebody else to r+ them :P</p>



<a name="211681043"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681043" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681043">(Sep 29 2020 at 20:39)</a>:</h4>
<p><span class="user-mention silent" data-user-id="116009">nikomatsakis</span> <a href="#narrow/stream/144729-wg-traits/topic/meeting.202020-09-29/near/211681009">said</a>:</p>
<blockquote>
<p>it's nice that it can be done progressively and in isolation</p>
</blockquote>
<p>That was my thought. Stepping stones.</p>



<a name="211681045"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681045" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Areredify <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681045">(Sep 29 2020 at 20:39)</a>:</h4>
<p>any time you want to do anything with binders that doesnt fit into the map paradigm it turns into a very wordy dance</p>



<a name="211681071"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681071" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681071">(Sep 29 2020 at 20:39)</a>:</h4>
<p>Okay, in this case, I'll put in the effort to do this</p>



<a name="211681077"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681077" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681077">(Sep 29 2020 at 20:40)</a>:</h4>
<p>And get some eyes on it</p>



<a name="211681126"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681126" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681126">(Sep 29 2020 at 20:40)</a>:</h4>
<p><span class="user-mention" data-user-id="216206">@lcnr</span> has r+ rights :)</p>



<a name="211681134"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681134" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681134">(Sep 29 2020 at 20:40)</a>:</h4>
<p><span class="user-mention silent" data-user-id="116009">nikomatsakis</span> <a href="#narrow/stream/144729-wg-traits/topic/meeting.202020-09-29/near/211681040">said</a>:</p>
<blockquote>
<p>better yet is we get somebody else to r+ them :P</p>
</blockquote>
<p>you can use me here</p>



<a name="211681148"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681148" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681148">(Sep 29 2020 at 20:40)</a>:</h4>
<p>heh :)</p>



<a name="211681155"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681155" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681155">(Sep 29 2020 at 20:40)</a>:</h4>
<p>hu :)</p>



<a name="211681156"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681156" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681156">(Sep 29 2020 at 20:40)</a>:</h4>
<p>good, I was feeling bad about volun-telling you</p>



<a name="211681173"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681173" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681173">(Sep 29 2020 at 20:40)</a>:</h4>
<p>I mostly just didn't want to put in the effort without people being on board</p>



<a name="211681192"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681192" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681192">(Sep 29 2020 at 20:40)</a>:</h4>
<p>I don't feel this requires an MCP</p>



<a name="211681247"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681247" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681247">(Sep 29 2020 at 20:41)</a>:</h4>
<p>Okay, with that, we're 40 minutes in</p>



<a name="211681270"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681270" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681270">(Sep 29 2020 at 20:41)</a>:</h4>
<p>So, I don't know if we really have time for a full design meeting on wellformedness</p>



<a name="211681295"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681295" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681295">(Sep 29 2020 at 20:41)</a>:</h4>
<p>tbh, I'm not <em>entirely</em> sure what we want to discuss</p>



<a name="211681305"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681305" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681305">(Sep 29 2020 at 20:41)</a>:</h4>
<p>I really should prepare these</p>



<a name="211681315"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681315" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681315">(Sep 29 2020 at 20:41)</a>:</h4>
<blockquote>
<p>I don't feel this requires an MCP</p>
</blockquote>
<p>Adding some kind of <code>map</code> to <code>Predicate</code> probably won't need one, there are some edge cases re rebinding the predicate but we will figure those out</p>



<a name="211681387"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681387" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681387">(Sep 29 2020 at 20:42)</a>:</h4>
<p>ah yeah I guess that method is on <code>Predicate</code> and not <code>Binders</code></p>



<a name="211681395"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681395" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681395">(Sep 29 2020 at 20:42)</a>:</h4>
<p>well, <em>something</em> in this direction</p>



<a name="211681403"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681403" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681403">(Sep 29 2020 at 20:42)</a>:</h4>
<p>(I'm not sure, is it?)</p>



<a name="211681423"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681423" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681423">(Sep 29 2020 at 20:42)</a>:</h4>
<p>it'd be nice to make it more elegant, but linking the binders to their source feels good to me</p>



<a name="211681463"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681463" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681463">(Sep 29 2020 at 20:43)</a>:</h4>
<p>anything that you two both like I imagine I will probably like :P</p>



<a name="211681494"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681494" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681494">(Sep 29 2020 at 20:43)</a>:</h4>
<p>re: this meeting, happy to discuss, but I can also go and use time to review a few PRs</p>



<a name="211681504"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681504" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681504">(Sep 29 2020 at 20:43)</a>:</h4>
<p>Okay, then when I make PRs, I'll r? <span class="user-mention" data-user-id="216206">@lcnr</span> and cc <span class="user-mention" data-user-id="116009">@nikomatsakis</span></p>



<a name="211681571"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681571" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681571">(Sep 29 2020 at 20:44)</a>:</h4>
<p>Is there anything anybody would like to discuss?</p>



<a name="211681625"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681625" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681625">(Sep 29 2020 at 20:44)</a>:</h4>
<p>If not, I'm good with ending a bit early</p>



<a name="211681739"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681739" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681739">(Sep 29 2020 at 20:45)</a>:</h4>
<p>Okay, I guess we'll end 15 minutes early</p>



<a name="211681763"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681763" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681763">(Sep 29 2020 at 20:45)</a>:</h4>
<p>And do the WF design meeting next week</p>



<a name="211681786"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681786" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681786">(Sep 29 2020 at 20:45)</a>:</h4>
<p>I'll try to actually prepare at least some discussion points for that</p>



<a name="211681794"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681794" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681794">(Sep 29 2020 at 20:45)</a>:</h4>
<p>I guess we are still waiting on an MCP second for <a href="https://github.com/rust-lang/compiler-team/issues/359">https://github.com/rust-lang/compiler-team/issues/359</a></p>



<a name="211681843"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681843" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681843">(Sep 29 2020 at 20:46)</a>:</h4>
<p>Yeah :/</p>



<a name="211681913"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681913" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681913">(Sep 29 2020 at 20:46)</a>:</h4>
<p>I thought about pleading the case a little bit more in the zulip topic</p>



<a name="211681925"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681925" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681925">(Sep 29 2020 at 20:46)</a>:</h4>
<p>but didn't get around to it</p>



<a name="211681960"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681960" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681960">(Sep 29 2020 at 20:46)</a>:</h4>
<p>I just left a few comments</p>



<a name="211681971"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681971" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681971">(Sep 29 2020 at 20:47)</a>:</h4>
<p>there <em>is</em> some uncertainty about the exact set of types that are affected</p>



<a name="211681976"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211681976" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211681976">(Sep 29 2020 at 20:47)</a>:</h4>
<p>probably best to discuss there</p>



<a name="211682003"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682003" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682003">(Sep 29 2020 at 20:47)</a>:</h4>
<p>I did briefly search the docs for "kind" when that was mentioned</p>



<a name="211682028"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682028" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682028">(Sep 29 2020 at 20:47)</a>:</h4>
<p>In almost all cases, it was pretty clear the distinction</p>



<a name="211682046"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682046" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682046">(Sep 29 2020 at 20:47)</a>:</h4>
<p>But maybe I'll post a summary</p>



<a name="211682101"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682101" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682101">(Sep 29 2020 at 20:48)</a>:</h4>
<p>(eek another thing I've assigned myself to do)</p>



<a name="211682154"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682154" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682154">(Sep 29 2020 at 20:48)</a>:</h4>
<p>what do you mean by "pretty clear the distinction"</p>



<a name="211682172"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682172" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682172">(Sep 29 2020 at 20:49)</a>:</h4>
<p>I thnk I would be in favor of NOT changing every single enum in the compiler that follows this pattern</p>



<a name="211682189"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682189" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682189">(Sep 29 2020 at 20:49)</a>:</h4>
<p>yes, that</p>



<a name="211682205"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682205" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682205">(Sep 29 2020 at 20:49)</a>:</h4>
<p>although I am wondering if people will find the rule clear</p>



<a name="211682214"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682214" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682214">(Sep 29 2020 at 20:49)</a>:</h4>
<p>Like, to me if felt "natural" which ones would and wouldn't</p>



<a name="211682233"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682233" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682233">(Sep 29 2020 at 20:49)</a>:</h4>
<p>generally it was just interned things</p>



<a name="211682330"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682330" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682330">(Sep 29 2020 at 20:50)</a>:</h4>
<p>Like, e.g. <code>ClosureKind</code>, doesn't make sense as <code>ClosureData</code>, because there's no data held</p>



<a name="211682455"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/144729-wg-traits/topic/meeting%202020-09-29/near/211682455" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Huey <a href="https://rust-lang.github.io/zulip_archive/stream/144729-wg-traits/topic/meeting.202020-09-29.html#211682455">(Sep 29 2020 at 20:51)</a>:</h4>
<p>Oh gosh, there are <em>so many</em> <code>kind</code>s</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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